The present invention relates to a system for illuminating nonemissive electronic displays, and more specifically, to a system for frontlighting a microencapsulated electrophoretic display.
The recent advent of nonemissive electronic displays has provided for inexpensive, low power, reflective displays. These displays have uses in a variety of applications such as advertising, information dissemination, education, and entertainment. However, because these displays are nonemissive, the effectiveness of these displays is limited to daytime use or to use in lit rooms. An illumination system which selectively illuminates the display media of such a display system is therefore desired.
Traditional displays (such as liquid crystal displays) typically are illuminated using backlighting. In backlit displays, light from a backlighting source passes through the back of the display via a light transmissive element, such as a light pipe, and is perceived by a viewer. This type of illumination can be used with liquid crystal displays because light can effectively pass through the display media. However, the utility of using backlighting with a nonemissive display, such as a microencapsulated electrophoretic display or rotating ball display, is limited because the display media in such a display is effectively opaque, acting as a barrier to light. In addition, various elements used to increase the uniformity of light passing through the light transmissive element, such as diffusers, decrease the amount of light ultimately reaching the viewer.
The present invention provides an illumination system to selectively illuminate a nonemissive electronic display, and in particular, provides a microencapsulated electrophoretic display in combination with a frontlighting illumination system. The present invention further provides display elements which can be tiled to create complex, selectively illuminated, three-dimensional structures.
In one embodiment of the invention, an illuminated nonemissive electronic display comprises a substrate having a first and a second surface. A microencapsulated electrophoretic display media is adjacent the first surface of the substrate and a light transmissive element is adjacent the second surface of the substrate. Light transmitted through the light transmitting illuminates the display media. In one embodiment of the invention, the light transmissive element is in communication with a light source transmitting light through the light transmissive element. In a further embodiment of the invention, the substrate is flexible. In still a further embodiment of the invention, the display is selectively illuminated through the use of a photodetector coupled to the light source. In this embodiment, the light source is activated when the level of ambient light detected by the photodetector drops below a selected value.
The invention also provides a tiled display comprising a plurality of substrates, each substrate having at least a first and second surface. A display media comprising microencapsulated electrophoretic display elements is adjacent the first surface of each of the substrates. A light transmissive element is adjacent the second surface of at least one substrate, and light transmitted through the light transmitting element is refractively distributed evenly through a face of the light transmissive element to be received by a viewer, thereby illuminating the display media. In one embodiment of the invention, the light source illuminates more than one substrate. In another embodiment of the invention, a plurality of light sources is provided. In a further embodiment of the invention, the light source(s) are coupled to a photodetector and are responsive to changes in ambient light.
The illumination system according to the present invention can be used to selectively illuminate multicharacter displays having a variety of three-dimensional shapes.